The present disclosure relates to imaging members and, more specifically, to photogenerating layers suitable for use with such imaging members.
In the art of electrophotography, an electrophotographic member having a photoconductive insulating layer on a conductive layer is imaged by first uniformly electrostatically charging the surface of the photoconductive insulating layer. The member is then exposed to a pattern of activating electromagnetic radiation such as light, which selectively dissipates the charge in the illuminated areas of the photoconductive insulating layer while leaving behind an electrostatic latent image in the non-illuminated areas. This electrostatic latent image may then be developed to form a visible image by depositing finely divided electroscopic toner particles, for example, from a developer composition, on the surface of the photoconductive insulating layer. The resulting visible toner image can be transferred to a suitable receiving member, such as paper. This imaging process may be repeated many times with reusable electrophotographic imaging members.
The electrophotographic imaging members, i.e., photoreceptors, may be in the form of plates, drums, flexible belts, etc. Electrophotographic photoreceptors may be prepared using either a single layer configuration or a multilayer configuration, but the multilayer arrangement is more common. Multilayered photoreceptors may include a substrate, a conductive layer, an optional hole blocking layer, an optional adhesive layer, a photogenerating layer (sometimes referred to as a “charge generation layer,” “charge generating layer,” or “charge generator layer”), a charge transport layer, an optional overcoating layer and, in some belt embodiments, an anticurl backing layer. In the multilayer configuration, the active layers of the photoreceptor are the charge generation layer (CGL) and the charge transport layer (CTL).
One type of multilayered photoreceptor has a layer of finely divided particles of a photoconductive inorganic compound dispersed in an electrically insulating organic resin. In U.S. Pat. No. 4,265,990, the disclosure of which is incorporated herein by this reference, a layered photoreceptor is disclosed having separate charge generation (photogenerating) layers and charge transport layers. The photogenerating layer is capable of photogenerating hole-electron pairs and injecting the photogenerated holes into the charge transport layer.
Dispersions utilized for forming photogenerating layers for photoreceptors prepared by dip coating processes frequently utilize high boiling point solvent systems, such as n-butyl acetate, xylene, or cyclohexanone. Methods for applying photogenerating layers utilizing these dispersions often do not include a drying step as the drying of any layer introduces extra cost, extra processing time, and possible defects in the production of the photoreceptor.
Other multi-layer photoreceptors include a photogenerating layer, a charge transport layer, and an overcoat layer. An example of such a photoreceptor is disclosed in U.S. Pat. No. 6,824,940, the contents of which are incorporated by reference herein. Such an overcoat layer may assist in extending the life of the photoreceptor by improving its wear resistance. However, in forming a photoreceptor which has an overcoat layer, it may be necessary to dry the photogenerating layer prior to application of any overcoat layer, as it is difficult to remove the solvent in a final drying step after application of an overcoat layer. Moreover, any solvent utilized in applying the photogenerating layer could penetrate through the upper layers thereby causing defects in the photoreceptor.
The cost to prepare photoreceptors increases with each step added to the manufacturing process. Improved methods for forming photoreceptors, including photogenerating layers used therein, are thus desirable.